1. Field of the Invention
The present invention pertains to an apparatus and process for separating emulsified viscous liquids and dissolved gases and, in particular, for separating dissolved gases and hydrocarbon oils from glycols or alkanolamines used to dehydrate or desulfurize natural and manufactured gases.
2. Background
In gas conditioning operations such as dehydration and desulfurization processes the presence of crude as well as refined lubricating oils, hydrocarbon condensates, dissolved gases and particulate matter in the gas conditioning liquids create very tight emulsions and cause formation of inseparable foams. These emulsions and foams interfere with the desired absorption and reaction processes, and also with regeneration and reuse of the conditioning solutions. For example, in the dehydration of natural gas using various ethylene glycols as the absorbents, hydrocarbon oils become emulsified in the liquid glycol. Of course, dissolved gases usually also accumulate in the glycol solution. Emulsified oils in glycol conditioning liquids can reach the level where the emulsion inverts to glycol-in-oil which creates hazardous and ineffective operating conditions in the equipment used to regenerate these solutions.
Another problem in gas dehydration and desulfurization processes is the formation of substantial quantities of stable foams which are virtually impossible to separate, and so are entrained with the treated gases. When these foams escape from the processing equipment with the treated gas there is not only a substantial loss of the gas conditioning solution but serious contamination of the gas pipeline system is also experienced. The formation of these foams is promoted by contaminants in the process flowstream such as iron sulfides, iron carbonates, corrosion inhibitors and carbonaceous materials. It is known that the use of clean gas conditioning or treating solutions reduces or eliminates foam formation. It is to this end that it is important to provide for separation of hydrocarbon oils and dispersed solids whih are not soluble in the conditioning liquid and to provide for degassing the conditioning liquid before it is fed to the regeneration process.
Although the various glycols and hydrocarbon oils have substantial differences in density, separation by settling is hindered by the high viscosity of these liquids. Ethylene glycol and other glycol liquids are quite viscous at ambient temperatures, even those temperatures experienced in moderate climates in all seasons. Where there is an oil-in-glycol emulsion, the glycol viscosity controls the settling rate. Retention time in the settling process and turbulence resulting from the design of the separating apparatus itself have posed problems in separating hydrocarbon oils from gas conditioning solutions in gas dehydration and desulfurization processes. Furthermore, the presence of the emulsifiers mentioned previously herein tends to stabilize emulsions and hinders the separation processes. Moreover, in most contemporary processes of this kind, little or no attempt has been made to lower fluid viscosities by means of temperature adjustment and control.
Accordingly, there has been a substantial need for improvement in operating techniques and apparatus for separating hydrocarbon oils and dissolved gas from liquids such as ethylene, diethylene, triethylene, and tetraethylene glycols as well as aqueous treating solutions for sour gas such as alkanolamines in aqueous solutions ranging from 10 to 65 percent by weight of amine. Heretofore, separation of immiscible liquids of this type, together with the separation of dissolved gases, has been generally unsatisfactory and need for improvement has been evident. Accordingly, the apparatus and process of the present invention represents an important improvement in regeneration of conditioning solutions for dehydration and desulfurization of various gases.